Internet provides a convenient channel for people to retrieve information. Through a browser window, an Internet user can easily access any one of the billions of web pages published on the Internet. Most web pages are written in a special computer language called “hypertext markup language” (HTML). However, a user must be very familiar with the HTML syntax in order to compose a web page having a desired look-and-feel. A typical unpleasant experience a web page author has with preparing an HTML file is that the HTML file, when rendered by a web browser, appears very differently from what the author expected. The web page author may spend many hours to debug and revise the HTML file so that when the HTML file is rendered by a web browser, it presents information or other content in the manner intended by the web page author.